Bump version to 1.3.0 and exclude tauri/ from Electron build

The Electron build was accidentally bundling the entire tauri/src-tauri/target
Rust build directory into app.asar (1.2GB!), inflating the installer to 304MB.
Added a files exclusion so Electron and Tauri builds stay independent.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "freight-calculator-pro",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "description": "Professional Freight Class Calculator",
   "main": "main.js",
   "scripts": {
@@ -17,6 +17,10 @@
   "build": {
     "appId": "com.freightcalc.pro",
     "productName": "Freight Calculator Pro",
+    "files": [
+      "**/*",
+      "!tauri/**"
+    ],
     "win": {
       "target": "nsis",
       "icon": "icon.ico"